Electronically controlled and pyrotechnic crew escape system and method

ABSTRACT

Pyrotechnic crew escape system having electronic switches and time delays for sequencing the firing of pyrotechnic devices in the ejection and recovery of a crew member from an aircraft.

United States Patent Van Kreuningen 1151 3,669,388 1451 June 13, 1972[54] ELECTRONICALLY CONTROLLED 2,570,295 10/1951 Vantine, Jr. ANDPYROTECHNIC CREW ESCAPE 3,067,973 l2/l962 Halsey et a]. ..244/|40 SYSTEMAND METHOD 3,270,217 8/1966 .244/151 x R 3,273,835 9/1966 H61: et al......244/l38 '12 hwmmr; Rudo" v. Kunming, Torrance c fifl 3,388,879 6/1968Pisano et a] .244] 152 3,470,029 9/1969 Meyers et 21.... 136/144 x 1Assisneei Explosive T hn logy, Fairfield, Calif. 3,567,158 3/1971 Coyle..244/122 8 [22] Filed: 1969 Primary Branflner-Milton Buchler [21] APPL872,023 Arm's/ant Examiner-Paul E. Sauberer Au0mey-F|ehr, Hohbach, Test,Albritton and Herbert 521 115.0. ..244/l38R [57 ABSTRACT 51 1m. (:1...B64d 25 00 Pyrotechnic crew escape system havmg electromc switches 58Field olSeru-ch ..244/13s-152, 122 R422 AH, and time delays sequencingthe fi i f pyrotechnic 133 R- 122 AB; 102/28; |35/83- 6 devices in theejection and recovery of a crew member from an aircraft. 56 RelereneesCited I 1 I BCIIIIII, 5 Dl'twlngngllm UNITED STATES PATENTS 2,501,5593/1950 Winzen et a] ..244/13s 1e 10 so 22 2o 51 25 I I2 I 7 HkRNESS 3THERMAL Q3 SEC ROCKET Palms; 1.64550 i iggg cATAPuLT a BATTERY DELAYGNITER cmcurr 79 CIRCUIT 36 48 I UPPER 23 27 13 43 r 31 02? SEC BRIDDLE32 UQUID 47 ELECTRONIC DELAY FIR! AMMONIA SWITCH 68 74 cmcurr 33 BATTERY1a LOWE 41 52 49 42 Q24 SEC BRIDDLE REEL CANOPY A8 46 44 DELAY FIRINGIGNITER nemrea I VELOCITYl ALTITUDE 73 cmcun ARM ssnson T ssusoaRESTRAINT 66 THRUSTER 53 63 64 ELECTRONIC L SEC SWITCH I DELAY 5 s1 /62PARACHUTE SEC MORTAR onoeus sun DELAY T FIRING FIRING CIRCUIT cmcun s172 I PATENTEDwnamz 3.669.388

I03 49 I02 T 52 53 I 0.06 0

54 i 3 I K I II6 [RI4I 1 M us '3 |3| '5 s 133 I v I 1221 I l I44 I w J ll I i F IG 4 l I PYROTECHNIC I DEVICE 77 i i Dl97 RIBZ SCR .9. 13 FlG 5TRIGGER 6- a Rl93 INVENTOR.

T I r Rudolf van Kreuningen PYROTECHNIC PYROTECHNIC BY DEVICE DEVICE i?ATTORNEYS ELECTRONIC-ALLY CONTROLLED AND PYROTECHNIC CREW ESCAPE SYSTEMAND METHOD BACKGROUND OF THE INVENTION This invention pertains generallyto escape systems for vehicles such as aircraft and more particularly toan electronic sequencing system and method for a crew escape system ofthe type utilizing pyrotechnic devices.

Crew escape systems have heretofore been provided in airplanes used formilitary purposes. A simple form of such a system consists of aparachute pack harnessed to the pilot or another crew member. While thissystem is adequate for escape out of slow flying aircraft at mediumaltitudes, it is unsatisfactory at low altitudes, extremely highaltitudes and/or high speeds. At low altitudes the parachute does nothave time to deploy its canopy, and at extremely high altitudes lack ofoxygen is a problem. At the high speeds attained by present dayaircraft, there is insufficient time for the crew member to jump clearof the aircraft without danger of being struck by the oncoming tailsection.

Various systems have been devised for overcoming the foregoing problems,and the present day military aircraft are commonly equipped with a seatejector system. In this system, the pilot or crew member is strappedinto his seat, and the man and seat are catapulted out of the aircraft.

Pyrotechnic devices are commonly used for ejecting the crewman and seatfrom the aircraft, for retarding the descent of the crewman and seat,and for deploying a parachute at the proper altitude. In such systems,it is important that the pyrotechnic devices be ignited in the propersequence and with the proper time intervals between firings. This timingmay be dependent on environmental conditions such as altitude andvelocity.

Heretofore, a common means for providing the time intervals inpyrotechnic crew escape systems has consisted of the use of pyrotechnicdelay devices such as timing fuses. Such devices cannot provide accuratetiming, and their reliability is undesirably low. Moreover, they cannotbe tested since testing necessarily involves destruction of the devices.

A pyrotechnic programming system utilizing conventionalelectromechanical time delay devices, known as unlatching switches, toprovide time intervals is described in US. Pat. No. 3,420,174, issued.Ian. 7, 1969. Such unlatching switches have mechanical contacts whichare adapted for opening after a predetermined time by the currentflowing through them. They are subject to contact bounce and chatter,and severe shock or vibration can cause them to switch inadvertently.Furthermore, such devices have relatively slow switching times.

There is, therefore, a need for a new and improved crew escape systemwhich includes means for overcoming the foregoing and other problemsencountered with systems heretofore provided.

SUMMARY AND OBJECTS OF THE INVENTION The present invention provides anelectronically controlled pyrotechnic sequencing system whereinelectronic switches and electronic time delays provide reliable firingof the pyrotechnic devices at accurately determined intervals.

It is in general an object of the invention to provide a new andimproved system and method for sequentially firing pyrotechnic devicesin a crew escape system.

Another object of the invention is to provide a system and method of theabove character which utilizes electronic switching means.

Another object of the invention is to provide a method and system of theabove character which utilizes electronic time delay means.

Additional objects and features of the invention will be apparent fromthe following description in which the preferred embodiment is set forthin detail in conjunction with the accompanying drawing.

2 BRIEF osscan nou or THE DRAWING FIG. 1 is a block diagram of oneembodiment of an electronic pyrotechnic sequencing system incorporatingthe present invention.

FIG. 2 is a circuit diagram of one embodiment of an electronic switchwhich can be used in the system shown in FIG. 1.

FIG. 3 is a circuit diagram of another embodiment of an electronicswitch which can be used in the system shown in FIG. 1.

FIG. 4 is a circuit diagram of one embodiment of a combined electronictime delay and firing circuit which can be used in the system shown inFIG. 1.

FIG. 5 is a circuit diagram of one embodiment of a firing circuitadapted for igniting a plurality of pyrotechnic devices.

DESCRIPTION OF THE PREFERRED EMBODIMENT The sequencing system shown inFIG. 1 comprises generally ejection sequencing means 11 adapted to becarried by an air craft or like vehicle, recovering sequencing means 12adapted to be ejected from the vehicle with a crew member, andelectrical connector means 13 removably connecting the ejectionsequencing means to the recovery sequencing means.

The ejection sequencing means includes a source of electrical power 16,a reel igniter 17, a canopy igniter 18, a rocket catapult igniter 19,and electronic delay means 20.

In the preferred embodiment, the power source 16 comprises a thermalbattery which is normally in an inactive state. In this inactive state,the battery's electrolyte is a crystalline material which must be meltedto activate the battery. Melting of the crystalline electrolyte isaccomplished by ignition of a pyrotechnic compound within the battery.The heat generated by this reaction liquifies the electrolyte, therebyenergizing the power source 16.

Both electrical and mechanical means are provided for causing the powersource 16 to assume its active state. The electrical means is designatedby the reference numeral 22 and includes a bridge wire adapted to beenergized by energy from the electrical system of the vehicle.Energization of the bridge wire detonates a percussion cap within thebattery. The mechanical means, designated by the reference numeral 23,includes a mechanical striker adapted for detonating the percussion cap.Detonation of the percussion cap ignites a heatproducing pyrotechnicdevice that produces liquification of the electrolyte. Activation of thefirst battery provides energy by which the batteries of subsequentlyenergized systems may be activated electrically. Alternately,subsequently energized systems may be activated by like mechanicalmeans.

The reel igniter 17 comprises an electrically ignited pyrotechnic devicethat actuates a power reel to strap the pilot or other crew member intohis seat. The canopy igniter 18 comprises an electrically firedpyrotechnic device that jettisons the canopy of the aircraft. The reeligniter I7 is connected directly to the power source 16 by circuits 26,27 and 28, and the canopy igniter I8 is connected directly to the sourceby circuits 26, 27 and 29. Thus, these igniters are adapted forstrapping the pilot or crewman into his seat and jettisoning the canopyat substantially the same time the power source 16 is activated.

The rocket catapult igniter 19 includes a firing circuit adapted toignite a conventional pyrotechnic device for ejecting the pilot or crewmember and his seat from the aircraft. The igniter 19 receives powerfrom the source 16 through the circuit 26, electronic delay means 20,and circuit 31. In the preferred embodiment, the firing circuit of thecatapult igniter is a capacity discharge circuit of the type illustratedin FIG. 4 and described hereinafter.

The electronic delay means 20 is of the type which is also illustratedin FIG. 4, and in the preferred embodiment, this delay means provides adelay on the order of 0.3 second. This delay permits the pilot orcrewman to be strapped into his seat and the canopy to be jettisonedbefore ejection occurs.

The connector means 13 of FIG. 1 provides releasable means forconducting electrical energy from the ejection sequencing means to therecovery sequencing means prior to ejection. it includes a conventionalelectrical connector comprising a plug 32 and a socket 33. The plug iselectrically connected to the circuit 27 in the ejector sequencingmeans. The socket 33 is associated with the recovery sequencing meansand is adapted to be ejected with that means. Preferably, this connectorshould be of a type which provides reliable electrical contact betweenthe plug and socket when they are engaged, yet permits them to bereadily separated by merely pulling them apart.

The recovery sequencing means 12 includes a source of electrical power36, electronic switches 37 and 38, environmental sensors 41 and 42, anda plurality of electronic delay means and firing circuits.

ln the preferred embodiment, the power source 36 includes a liquidammonia battery having an inactive state and an ac tive state. Liquidammonia is used as the electrolyte in this battery and is retained outof contact with the plates during the inactive state. The batteryincludes a bridge wire and a small pyrotechnic device for releasing theammonia to the plates in response to an electrical signal. The bridgewire is connected to the socket 33 by a circuit 43.

If desired, redundancy can be provided by using a plurality of liquidammonia batteries in the power source 36. These batteries can beconnected in parallel and isolated from each other by conventional meanssuch as diodes.

An arm restraint thruster 44 of conventional design is provided forrestraining the arms and legs of the pilot or crewman during ejectionfrom the plane. Such devices typically include straps adapted forengaging the arms and legs and securing them to the ejection seat. Inthe preferred embodiment, this device is pyrotechnically activated andis connected to the socket 33 by circuits 43, 46.

The output of the power source 36 is connected to the electronic switch37 by a circuit 47. The switch 37 is a latching single pole, singlethrow switch of the type shown in FIG. 2 and described hereinafter indetail. Actuation of this switch causes power to be delivered to thecircuits 48 and 49.

The circuit 48 is connected to a firing circuit 51 which is adapted fordeploying a pyrotechnically activated stabilization system, such as oneproduced by Douglas Aircraft, and commonly known as Stapac. The Stapacfunctions to stabilize and maintain the pilot or crewman and his seat ina proper orientation following ejection from the aircraft by the actionof a pyrotechnically actuated, gas powered gyroscopic turbine working inconjunction with a small rocket thruster located beneath the seat. Thefiring circuit 51 can include a capacitive discharge circuit of the typeillustrated in FIG. 4.

The circuit 49 is connected to the circuits 52 and S3 for deliveringpower to the environmental sensors 41 and 42, respectively. The sensor41 includes a conventional velocity sensitive switch having a pair ofcontacts adapted to be closed below a predetermined velocity and to beopen above that velocity. The output of the velocity sensor 41 isconnected to one control input of the electronic switch 38 by a circuit54.

The sensor 42 includes an altitude sensitive switch having a pair ofcontacts adapted to be open below a predetermined altitude and to beclosed above that altitude. The output of the altitude sensor 42 isconnected to a second control input of the electronic switch 38 by acircuit 56.

The electronic switch 38 is a multiple pole electronic switch of thetype illustrated in FIG. 3 and described hereinafter in detail. In thepreferred embodiment, this switch is characterized in that its switchingaction is independent of the presence or absence of power on its poles.Thus, once switched to a given position, the switch 38 will remain inthat position even though the power is removed from the poles of theswitch.

Means is provided for retarding the descent of the ejected pilot orcrewman. This means includes a conventional drogue gun adapted to betired by means ofa drogue gun firing circuit 58. This circuit caninclude a capacitive discharge firing circuit of the type hereinafterdescribed and is connected for receiving a trigger signal from theelectronic switch 38 through a circuit 59.

One pole of the electronic switch 38 is connected through a circuit 61to a circuit 62. The other pole of the switch is connected by a circuit63 to an electronic delay circuit 64. This delay circuit can be of thetype shown in FIG. 4. In the preferred embodiment, it provides a timedelay on the order of 0.51 second. The output of the delay means 64 isapplied to the circuit 62 through a circuit 66.

The circuit 62 is connected to a plurality of delay circuits 67, 68, 69,70. These circuits can be electronic delay circuits of the type shown inFIG. 4, and in the preferred embodiment they provide time delays on theorder of 0.04 second, 0.24 second, 0.27 second, and 1.84 seconds,respectively.

The outputs of the delay circuits 67, 68, 69, and 70 are connectedthrough circuits 72, 73, 74, and 75, respectively, to firing circuits77, 78, 79, and 80. These firing circuits can all be of the capacitivedischarge type illustrated in FIG. 4. Each is adapted for firing apyrotechnic device to initiate a particular phase in the recovery of thepilot or crewman. Thus, the firing circuit 77 causes the main parachuteto be deployed, circuits 78 and 79 cause release of the upper and lowerbridles for the drogue gun, and the circuit 80 releases the pilot orcrewman from the seat. Because of the different time delays of thecircuits 67 to 70, the phases of the recovery operation are initiated ina predetermined sequence, separated by predetermined time intervals.

FIG. 2 shows a preferred embodiment of the single pole, single throwelectronic switch 37. This switch includes an input terminal 82 adaptedto be connected to the circuits 48 and 49. Conduction between theterminals 82 and 84 is controlled by a conventional switching transistorQ84. The transistor 084 is controlled by another conventional switchingtransistor 086 which in turn is controlled by a silicon controlledrectifier SCR87. This SCR is triggered by means of a normally openswitch 888. This switch is attached to the ejection seat of the pilot orcrewman and is adapted to be closed by the ejection of the seat from theaircraft.

Under normal conditions, that is prior to ejection, power is ap liedbetween the input terminal 82 ad ground, and there is no output at theterminal 84. During this time, there is no trigger signal applied to thegate 89 of the SCR, and the SCR remains nonconductive. Base current issupplied to the transistor Q86 through a resistor R91 and diode D92,saturating the transistor 086. The base 93 of the transistor 084 isgrounded through the transistor Q86, holding the transistor Q84 in itsnonconductive state.

Closing of the switch S88 causes a trigger signal to be applied to thegate 89 of the SCR, turning on the SCR. This grounds the base 94 of thetransistor Q86, turning that transistor off. The transistor Q84 is nowturned on by base current flowing through resistor R96, and the voltageat the output terminal 84 will be nearly equal to the voltage at theinput terminal 82. Because of the latching action of the SCR, thetransistor Q86 will remain off and the transistor 084 will remain on aslong as power is present at the input terminal 82.

As illustrated in FIG. 3, the electronic switch means 38 includes a pairof output poles 101 and 102 adapted to be connected to the circuits 6]and 63, respectively. This switch means also includes an input pole 103adapted to be connected for receiving power from the source 36. A firstswitching transistor 0104 is connected intermediate the input pole 103and output pole 101 for controlling the flow of current between thesepoles. Likewise, a second switching transistor 0106 is provided forcontrolling the flow of current between the poles 103 and 102.

The switching means 38 also includes electronic signal conditioningmeans for providing control signals to determine the states ofconductivity of the transistors 0104 and 0106. The signal conditioningmeans includes a silicon controlled rectifier SCR107 and transistors0108, Q109, Q1 11, and G112. The

collector 113 of the transistor 0112 is connected to the base 114 bymeans of a conductor 116, making the state of conductivity of thetransistor 0106 dependent upon the state of the transistor 01 12.

The collector 117 of the transistor 111 is connected to the base 118 ofthe transistor 0104 by a conductor 1 19 and to the base 121 of thetransistor 0112 by a resistor R122 and diode D123. Thus, the states ofthe transistors 0104 and 0112 are adapted to be determined by the stateof the transistor 01 1 1.

The base 124 of the transistor 0111 is connected to the collector 126 ofthe transistor 0109 by a conductor 127, adapting the transistor 01 1 1for control by the transistor 0109.

The base 128 of the transistor 0109 is connected to the anode 129 of thesilicon controlled rectifier SCR107 through a diode 131. The junction ofthe diode 131 and SCR anode 129 is connected to a source of positivevoltage through a resistor 132. The cathode 133 of the SCR is connectedto ground. Thus, the state of the transistor 0109 is controlled by theSCR.

The gate 134 of the SCR is connected to the collector 136 through aresistor 137 and a diode 138, adapting the SCR for control by thetransistor 0108, or through R142 by the altitude sensor 42.

The velocity sensor 41 and altitude sensor 42 are connected to thesignal conditioning means in such manner that the states of theswitching transistors 0104 and 0106 are primarily controlled by thesesensors.

The input of the velocity sensing switch 41 is connected for receivingpower from the electronic switch 37 through the circuits 49 and 52. Theoutput of the velocity sensor 41 is connected to the base 139 of thetransistor 108 through the circuit 54 and a resistor 141. Thus, thestate of the transistor 0108 is determined by the velocity sensor.

The input of the altitude sensing switch 42 is connected for receivingpower from the switching means 37 through the circuits 49 and 53. Theoutput of the altitude sensor is connected to the gate 134 of thesilicon controlled rectifier SCR107 through a resistor 142 and to thebase 121 of the transistor 112 through a resistor 143. Thus, thealtitude sensor is adapted for controlling the states of both the SCRand the transistor 0112.

The electronic switch 38 also includes means for triggering the droguegun firing circuit 58. Thus, the circuit 59 is connected to the junctionof the resistor 137, the resistor 142, and the SCR gate 134 by means ofa conductor 144.

Operation of the electronic switch 38 can now be described briefly asfollows. Initially, let it be assumed that the ejected pilot or crewmanis at a low altitude, in which case the contacts of the altitude sensingswitch 42 remain open. At low velocities, the contacts of the velocitysensing switch 41 will be closed, and base drive will be applied to thetransistor 0108 through the resistor 141, turning this transistor on.The SCR gate 134 is grounded through the resistor R137, diode D138, andtransistor 0108, thereby maintaining the SCR in its nonconductive state.With the SCR turned off, the transistor 0109 receives base drive throughthe resistor R130 and is turned on. The base 124 of the transistor 0111is grounded through the transistor 0109; hence, this transistor is 00'.Since the transistor 0111 is off, the transistor 0104 is on, and anoutput signal appears at the terminal 101 and in the circuit 61. Also,with the transistor 011 1 off, the transistor 0112 is on, and thetransistor 0106 is off, so there is no output at the terminal 102 or inthe circuit 63.

At high velocities, the velocity sensing switch 41 opens, and thetransistor 0108 is turned off. A positive voltage is applied to the SCRgate 134 through the resistor R140, diode D138, and resistor R137,triggering the drouge firing circuit 58 and also triggering the SCR intoconduction. The base 128 of the transistor 109 is grounded, turning thistransistor off and tuming the transistor 0111 on. With the transistor0111 on, the transistor 0112 is turned off, and the transistor 0106 isturned on, with a signal appearing at the output terminal 102 and in thecircuit 63. With the transistor 01 11 turned on, the

transistor 0104 is turned off, and there 101 or in the circuit 61.

At high altitudes, the contacts of the altitude sensing switch 42 areclosed, and power is applied to the drouge gun firing circuit throughthe resistor R142 and conductor 144. Current also flows through theswitch 42, and resistor R143 to the base 121 of the transistor 0112,turning this transistor on. With the transistor 01 12 turned on in thismanner, the transistors 0104 and 0106 are both turned off, and there isno signal at either of the poles 101, 102 or in the circuits 6!, 63.

It is to be noted that once the silicon controlled rectifier SCR107 hasbeen triggered, it remains turned on as long as power is applied to itthrough the resistor 132. This tends to latch the switch 38 in thecondition whereby 0104 is turned 01? and 0106 is turned on, with anoutput appearing at the terminal 102 and in the circuit 63. Further, itis to be noted that the circuit permits the transistors 0104 and 0106 tobe switched and maintained in a given state independently of thepresence of power at the pole 103.

FIG. 4 illustrates preferred embodiments of an electronic time delaycircuit 151 and a capacitive discharge firing circuit 152 which can beutilized in the present invention.

The delay circuit 151 includes a pair of input terminals 153 and 154adapted to be connected to a source of dc voltage. A resistor R156 andZener diode Zd157 are connected in series between the terminals 153 and154 to provide a source of constant voltage across the Zener diode. Aresistor R158 and a capacitor C159 are connected in series across theZener diode. The junction of the resistor R158 and capacitor C159 isconnected to the emitter 161 of a unijunction transistor 0162. The bases163 and 164 of the unijunction transistor are connected to the source ofvoltage by resistors R166 and R167, respectively. The junction of thebase 164 and resistor R167 is connected to an output terminal 168.

Operation of the electronic delay circuit can now be described brieflyas follows. With zero voltage applied to the input terminals 153, 154there will be no output at the terminal 168. When the terminal 153 ismade positive with respect to the tenninal 154, the capacitor C159begins to charge through the resistor R158. When the voltage across thecapacitor C159 reaches the threshold voltage of the transistor 0162,this transistor tires and a positive voltage appears at the outputterminal 168. The rate at which the capacitor C159 charges is determinedprimarily by the values of the capacitor and the resistor R158.

The capacitive discharge firing circuit 152 includes a resistor R171, acapacitor C172, and a silicon controlled rectifier SCR173. The resistorR171 and capacitor C172 are com nected in series to a source of dcvoltage such as that applied to the input terminals 153 and 154 of thedelay circuit 151. The junction of the resistor and capacitor isconnected to the anode 174 of the silicon controlled rectifier, and thecathode 176 of the SCR is connected to one input terminal of apyrotechnic device 177 by a circuit 178. The other input terminal of thepyrotechnic device is connected to the side of the capacitor oppositethe resistor R171. The SCR gate 179 is connected to a trigger signalsource, such as the output terminal 168 of the time delay circuit 151.

Operation of the firing circuit 152 can be described briefly as follows.Application of a voltage across the resistor R171 and capacitor C172causes the capacitor to charge. When a trigger signal is applied to theSCR gate 179, the SCR fires, discharging the capacitor C172 into thepyrotechnic device 177, thing that device.

The electronic capacitive discharge firing circuit has been found toprovide a reliable means of igniting pyrotechnic devices from a batterycapable of providing only a small fraction of the necessary firingcurrent. In the circuit shown in FIG. 4, the resistor R171 providesmeans for limiting the flow of current through the SCR after thepyrotechnic device has fired. Thus, if the firing of the device shouldproduce a short circuit, the resistor R171 prevents excessive drain onthe battery.

is no output at the pole FIG. shows a capacitive discharge circuit forfiring two pyrotechnic devices from a single trigger signal. Thiscircuit is generally similar to the firing circuit shown in FIG. 4except that it includes two resistors R181 and R182, two capacitors C183and C184, and two silicon controlled rectifiers SCRI86 and SCR187. Thecapacitor C183 charges through the resistor R181 and is dischargedthrough the silicon controlled rectifier SCR186 into the pyrotechnicdevice 188. The capacitor C184 is charged through the resistor R182 anddischarged through the silicon controlled rectifier SCR187 into thepyrotechnic device 189. The gates of the SCRs are connected to a commontrigger terminal 191 by resistors R192 and R193. These resistors providepartial isolation of the gates of the SCRs. Diodes D196, D197 areconnected between the resistors R181, R 182 and the source of voltage toprovide further isolation between the SCRs and assure that a short ineither pyrotechnic device will not prevent the other from firing.

Operation of the overall system of the present invention can now bedescribed briefly. Initially, let it be assumed that a pilot wishes toeject himself from an aircraft flying at low velocity and low altitude.Activation of the thermal battery 16 causes power to be appliedimmediately to the reel igniter l7 and canopy igniter l8, strapping thepilot into his seat andjettisoning the canopy. At the same time, poweris applied to the arm restraint thruster 44, and the pilots arms andlegs are strapped down. Power is also applied to the electronic delaycircuit 20, and after a 0.3 second delay the catapult rocket is ignited,ejecting the pilot and his seat from the aircraft.

Activation of the terrnal battery 16 also causes power to be applied tothe bridge wire of the liquid ammonia battery 36, activating thatbattery. Ejection of the pilot and his seat causes the switch S88 to beactuated, turning on the electronic switch 37 and supplying power to theStapac firing circuit 51 and to the velocity sensor 41 and altitudesensor 42. The circuit 51 tires immediately, deploying the stabilizationsystem.

With the aircraft at low velocity and low altitude, the velocity switch41 is closed, and the altitude switch 42 is opened. This conditions theelectronic switch 38 such that an output signal is applied to thecircuit 61, but not to the circuit 63. There is no output to the circuit59 in this condition, and the drogue gun is not fired. The signal in thecircuit 61 is transferred directly to the circuit 62 to actuate thedelay circuits 67, 68, 69 and 70. The main parachute is deployed 0.04second after the circuit 62 is energized, the lower and upper drogue gunbridles are released after delays of 0.24 second and 0.27 second,respectively, and the seat is released afler a delay of 1.84 seconds.

If the pilot were ejected at low altitude and high velocity, both of theenvironmental switches would be open. This would condition theelectronic switch such that the drogue gun would be tired and therewould be an output in the circuit 63. The signal in this circuitactivates the timing circuit and after a delay of 0.51 second produces asignal in the circuit 62. Thereafter, the parachute, drogue gun bridle,and seat harness firing circuits are fired in the same sequence asabove.

At high altitudes, the altitude sensing switch 42 remains closed, andthe electronic switch 38 is conditioned such that the drogue gun isfired, but there is no output to either circuit 61 or circuit 63. Whenthe pilot reaches a low altitude, the switch 42 opens and the sequencingof the parachute, drogue gun bridle, and seat harness firing circuits iscontrolled by the velocity sensor 41 in the manner described above.

lt is apparent from the foregoing that a new and improved system andmethod for sequentially firing pyrotechnic devices in a crew escapesystem has been provided. This system and method utilize electronicswitches to provide fast and reliable firing of the pyrotechnic devicesand electronic time delays to provide accurate time intervals.

I claim:

1. In a crew escape system of the type including an electrical powersource and a plurality of pyrotechnic devices adapted to be ejected witha crew member from a vehicle, electronic switch means connectedintermediate the power source and pyrotechnic devices for selectivelycontroling the flow of power from said source to said devices for firingsaid devices, said electronic switch means including a plurality ofsolid state switching devices each having terminals connected intermediate said power source and one of said pyrotechnic devices, each ofsaid switching devices also having a conductive state in which power canflow between its terminals and a nonconductive state in which such powercannot flow, and electronic signal conditioning means connected to saidswitching devices for supplying control signals to said devices forselectively switching them between their conductive and nonconductivestates and maintaining them in such states independently of the presenceof absence of power at said terminals.

2. A system as in claim 1 together with environmental sensing meansresponsive to predetermined environmental conditions such as altitudeand velocity, and means connecting said sensing means to said signalconditioning means in such manner that the control signals supplied tosaid switching devices are determined by said environmental conditions.

3. in a crew escape system of the type including an electrical powersource and at least one pyrotechnic device adapted to be ejected with acrew member from a vehicle, electronic switch means connectedintermediate the power source and pyrotechnic device, and capacitivedischarge means connected for firing said pyrotechnic device, saidcapacitive discharge means including a capacitor connected to said powersource for receiving current therefrom, solid state switch means adaptedfor connecting said capacitor to said pyrotechnic device in response toa trigger signal from said electronic switch means, and current limitingmeans intermediate said capacitor and said power source to preventexcessive power drain from said source following the firing of saidpyrotechnic device.

4. A system as in claim 3 together with an additional pyrotechnic deviceand additional capacitive discharge means of the character described inclaim 3 for firing said additional device from the same trigger signalthat fires the first named device, and diode means connectedintermediate said power source and the capacitor in each discharge meansto provide isolation between the first named and additional pyrotechnicdevices.

5. In a crew escape system for ejecting a crew member from a vehicle, afirst battery and at least one pyrotechnic device adapted to be ejectedwith the crew member, said battery having active and inactive states andbeing adapted for assuming the active state in response to an electricalsignal, electronic switch means adapted to be ejected with the crewmember, said electronic switch means being connected intermediate thebattery and pyrotechnic device for controlling the flow of power fromsaid battery to said device, ejection sequencer means carried by thevehicle for applying an electrical signal to said battery, and meansreleasably connecting said battery electrically to said ejectionsequencer means, said ejection sequencer means including a secondbattery having inactive and active states and being adapted formechanical and electrical activation, electrically ignited rocketcatapult means for ejecting the crew member from the vehicle, andelectronic time delay means connected intermediate said second batteryand said catapult means for delaying the ejection of said crew memberfor a predetermined interval of time after activation of said secondbattery.

6. In an electronically controlled pyrotechnic system for enabling acrew member to escape from a vehicle, electronic ejection sequencingmeans carried by said vehicle, electronic recovery sequencing meansadapted to be ejected from the vehicle with due crew member, andelectrical means releasably connecting said ejection sequencing means tosaid recovery sequencing means, said ejection sequencing means includingbattery means having active and inactive states and being adapted formechanical and electrical activation, means connecting the output ofsaid battery means to said electrical means, electrically ignitedpyrotechnic means for ejecting the crew member from the vehicle, andelectronic delay means connected intermediate said battery means andsaid pyrotechnic means for delaying the ignition of said pyrotechnicmeans for a predetermined time interval after activation of said batterymeans.

7. In an electronically controlled pyrotechnic system for enabling acrew member to escape from a vehicle electronic ejection sequencingmeans carried by said vehicle, electronic recovery sequencing meansadapted to be ejected from the vehicle with the crew member, andelectrical means releasably connecting said ejection sequencing means tosaid recovery sequencing means, said recovery sequencing means includinga battery having active and inactive states, said battery beingconnected to said electrical means for receiving a signal from saidejection sequencing means for causing said battery to assume its activestate, latching electronic switch means electrically connected to saidbattery and adapted to be triggered as the recovery sequencing means isejected from the vehicle, a plurality of pyrotechnic devices, multiplepole electronic switch means connected intermediate said battery andsaid pyrotechnic devices for selectively controlling the flow of powerto said devices, electronic time delay means connected intermediate saidmultiple pole electronic switch means and said pyrotechnic devices forsequencing the firing of said devices, and electronically controlledfiring means intermediate said delay means and pyrotechnic means adaptedfor receiving and storing energy from said battery and delivering saidenergy to the pyrotechnic devices in response to signals from said delaymeans.

8. In a crew escape system, a liquid amonia battery, at least onepyrotechnic device adapted to be ejected with a crew member from avehicle, said battery having active and inactive states and beingadapted for assuming the active state in response to an electricalsignal, electronic switch means connected intermediate the battery andpyrotechnic device for controlling the flow of energy from said batteryto said device, ejection sequencer means carried by the vehicle forapplying an electrical signal to said battery to activate the same, andmeans releasably connecting said battery electrically to said ejectionsequencer means before said battery is activated.

t t I! i l

1. In a crew escape system of the type including an electrical powersource and a plurality of pyrotechnic devices adapted to be ejected witha crew member from a vehicle, electronic switch means connectedintermediate the power source and pyrotechnic devices for selectivelycontroling the flow of power from said source to said devices for firingsaid devices, said electronic switch means including a plurality ofsolid state switching devices each having terminals connectedintermediate said power source and one of said pyrotechnic devices, eachof said switching devices also having a conductive state in which powercan flow between its terminals and a nonconductive state in which suchpower cannot flow, and electronic signal conditioning means connected tosaid switching devices for supplying control signals to said devices forselectively switching them between their conductive and nonconductivestates and maintaining them in such states independently of the presenceof absence of power at said terminals.
 2. A system as in claim 1together with environmental sensing means responsive to predeterminedenvironmental conditions such as altitude and velocity, and meansconnecting said sensing means to said signal conditioning means in suchmanner that the control signals supplied to said switching devices aredetermined by said environmental conditions.
 3. In a crew escape systemof the type including an electrical power source and at least onepyrotechnic device adapted to be ejected with a crew member from avehicle, electronic switch means connected intermediate the power sourceand pyrotechnic device, and capacitive discharge means connected forfiring said pyrotechnic device, said capacitive discharge meansincluding a capacitor connected to said power source for receivingcurrent therefrom, solid state switch means adapted for connecting saidcapacitor to said pyrotechnic device in response to a trigger signalfrom said electronic switch means, and current limiting meansintermediate said capacitor and said power source to prevent excessivepower drain from said source following the firing of said pyrotechnicdevice.
 4. A system as in claim 3 together with an additionalpyrotechnic device and additional capacitive discharge means of thecharacter described in claim 3 for firing said additional device fromthe same trigger signal that fires the first named device, and diodemeans connected intermediate said power source and the capacitor in eachdischarge means to provide isolation between the first named andadditional pyrotechnic devices.
 5. In a crew escape system for ejectinga crew member from a vehicle, a first battery and at least onepyrotechnic device adapted to be ejected with the crew member, saidbattery having active and inactive states and being adapted for assumingthe active state in response to an electrical signal, electronic switchmeans adapted to be ejected with the crew member, said electronic switchmeans being connected intermediate the battery and pyrotechnic devicefor controlling the flow of power from said battery to said device,ejection sequencer means carried by the vehicle for applying anelectrical signal to said battery, and means releasably connecting saidbattery electrically to said ejection sequencer means, said ejectionsequencer means including a second battery having inactive and activestates and being adapted for mechanical and electrical activation,electrically ignited rocket catapult means for ejecting the crew memberfrom the vehicle, and electronic time delay means connected intermediatesaid second battery and said catapult means for delaying the ejection ofsaid crew member for a predetermined interval of time after activationof said second battery.
 6. In an electronically controlled pyrotechnicsystem for enabling a crew member to escape from a vehicle, electronicejection sequencing means carried by said vehicle, electronic recoverysequencing means adapted to be ejected from the vehicle with the crewmember, and electrical means releasably connecting said ejectionsequencing means to said recovery sequencing means, said ejectionsequencing means including battery means having active and inactivestates and being adapted for mechanical and electrical activation, meansconnecting the output of said battery means to said electrical means,electrically ignited pyrotechnic means for ejecting the crew member fromthe vehicle, and electronic delay means connected intermediate saidbattery means and said pyrotechnic means for delaying the ignition ofsaid pyrotechnic means for a predetermined time interval afteractivation of said battery means.
 7. In an electronically controlledpyrotechnic system for enabling a crew member to escape from a vehicleelectronic ejection sequencing means carried by said vehicle, electronicrecovery sequencing means adapted to be ejected from the vehicle withthe crew member, and electrical means releasably connecting saidejection sequencing means to said recovery sequencing means, saidrecovery sequencing means including a battery having active and inactivestates, said battery being connected to said electrical means forreceiving a signal from said ejection sequencing means for causing saidbattery to assume its active state, latching electronic switch meanselectrically connected to said battery and adapted to be triggered asthe recovery sequencing means is ejected from the vehicle, a pluralityof pyrotechnic devices, multiple pole electronic switch means connectedintermediate said battery and said pyrotechnic devices for selectivelycontrolling the flow of power to said devices, electronic time delaymeans connected intermediate said multiple pole electronic switch meansand said pyrotechnic devices for sequencing the firing of said devices,and electronically controlled firing means intermediate Said delay meansand pyrotechnic means adapted for receiving and storing energy from saidbattery and delivering said energy to the pyrotechnic devices inresponse to signals from said delay means.
 8. In a crew escape system, aliquid amonia battery, at least one pyrotechnic device adapted to beejected with a crew member from a vehicle, said battery having activeand inactive states and being adapted for assuming the active state inresponse to an electrical signal, electronic switch means connectedintermediate the battery and pyrotechnic device for controlling the flowof energy from said battery to said device, ejection sequencer meanscarried by the vehicle for applying an electrical signal to said batteryto activate the same, and means releasably connecting said batteryelectrically to said ejection sequencer means before said battery isactivated.